Systems and methods for modeling both unobstructed and obstructed portions of a catheter

ABSTRACT

Electrical mapping system and methods are disclosed for modeling both unobstructed and obstructed portions of a catheter. An exemplary system includes a catheter body comprising a distal portion and a proximal portion, the catheter body supporting a plurality of electrodes electrically connected to an output device. The system also includes a rendering component operatively associated with the output device. The rendering component receives raw data from the plurality of electrodes and generates a plurality of images based on the raw data. Then the rendering component overlays the plurality of data images on one another to generate a three-dimensional image representing both the internal tissue and a visible portion of the catheter body. The system also includes an enhancement component which retrieves positional data for the catheter body and overlays a silhouette of at least one obstructed portion of the catheter body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing based upon internationalapplication no. PCT/US2008/087269 (the '269 application), filed 17 Dec.2008, which claims the benefit of and priority to United Statesprovisional application no. 61/014,135, filed 17 Dec. 2007 (the '135application). The '269 application and '135 application are both herebyincorporated by reference as though fully set forth herein.

BACKGROUND OF THE INVENTION

a. Field of the Invention

The instant invention relates to electrical mapping of a patient'sheart. In particular, the instant invention relates to a catheter whichgathers data for high resolution cardiac mapping and associatedcomponents which generate a model showing a graphical representation ofthe heart and catheter even if portions of the catheter would otherwisebe obstructed from view.

b. Background Art

A number of mapping and navigation options are available for electricalmapping of a patient's heart, for example, to navigate a catheter to adesired site within the patient's heart for an ablation or other medicalprocedure. For example, the EnSite NavX® utility is integrated into theEnsite® Advanced Mapping System (available from St. Jude Medical, Inc.),and provides non fluoroscopic navigation of electrophysiology catheters.

The methodology implemented by this mapping system is based on theprinciple that when electrical current is applied across two surfaceelectrodes, a voltage, gradient is created along the axis between theelectrodes. Although any suitable number of electrodes may be utilized,typically six surface electrodes are placed on the body of the patientand in three pairs: anterior to posterior, left to right lateral, andsuperior (neck) to inferior (left leg). The three electrode pairs formthree orthogonal axes (X-Y-Z), with the patients heart being at leastgenerally at the center.

These six surface electrodes are connected to the Ensite® AdvancedMapping System, which alternately sends an electrical signal througheach pair of surface electrodes to create a voltage gradient along eachof the three axes, forming a transthoracic electrical field.Conventional electrophysiology catheters may be connected to the Ensite®Advanced Mapping System and advanced to the patient's heart. As acatheter enters the transthoracic field, each catheter electrode sensesvoltage, timed to the creation of the gradient along each axis. Usingthe sensed voltages compared to the voltage gradient on all three axes,the EnSite NavX® utility calculates the three-dimensional position ofeach catheter electrode. The calculated position for the variouselectrodes occurs simultaneously and repeats many times per second(e.g., about 93 times per second).

The Ensite® Advanced Mapping System displays the located electrodes ascatheter bodies with real-time navigation. By tracking the position ofthe various catheters, the EnSite NavX® utility providesnon-fluoroscopic navigation, mapping, and creation of chamber modelsthat are highly detailed and that have very accurate geometries. In thelatter regard, the physician sweeps an appropriate catheter electrodeacross the heart chamber to outline the structures by relaying thesignals to the computer system that then generates the 3-D model. This3-D model may be utilized for any appropriate purpose, for instance tohelp the physician guide an ablation catheter to a heart location wheretreatment is desired.

In order to generate an accurate and highly detailed map of a patient'sheart, a large amount of data is required. Accordingly, an electrodecatheter may be swept across various surfaces of the heart whileobtaining data as described above. In order to accelerate this mappingdata acquisition and/or increase the volume of data available formapping, a number of high-density electrode catheters have beendeveloped or proposed. Generally, these include a number of electrodesin an array in relation to a catheter body so as to substantiallysimultaneously obtain many mapping data points for a correspondingsurface of cardiac tissue proximate to the catheter body. For example,these electrodes may be deployed along the length of a section of thecatheter body that has a coil or other three-dimensional configurationso as to provide the desired spatial distribution of the electrodes.Alternatively, the electrodes may be disposed on a number of structuralelements extending, from a catheter body, e.g., in the form of a basketor a number of fingers.

Once the mapping data has been acquired, software may be implemented togenerate multiple surface images, which when combined, comprise athree-dimensional image of the patient's heart. This image can bedisplayed on a suitable output device in real-time so that the physiciancan “see” the patient's heart and the catheter for properly positioningthe catheter at a work site within the patient's heart for a medicalprocedure (e.g. an ablation procedure). However, the renderingtechniques used to generate the three-dimensional image of the patient'sheart necessarily result in portions of the catheter being obscured. Forexample, the catheter may be physically located “behind” the surface ofthe heart being viewed, and therefore portions of the catheter may beobscured from view in the rendered three-dimensional image. Or forexample, the catheter may be drawn behind other objects being displayedfor the physician, such as labels or other graphical entities.

By way of illustration, Ensite® Advanced Mapping System creates computermodels of heart chambers which are then displayed graphically on thecomputer screen. Simultaneously, one or more catheters are alsodisplayed in the corresponding position and orientation with respect tothe heart chambers. Because the catheters are usually inside the heartchambers, the display of these catheters can be completely or partiallyobstructed (i.e., obscured from view) by the simultaneous or overlappingdisplay of the heart chamber walls. The catheter can be additionallyobscured from view by other graphical entities, such as labels, lesions,anatomical markers, and other catheters. Although the physician may havea good idea of where the catheter is within the heart, there exists aneed to provide more clarity for the physician.

BRIEF SUMMARY OF THE INVENTION

It is desirable to be able to provide high-quality images of thepatient's heart and catheter for the physician to view during a medicalprocedure. It is further desirable to be able to provide the physician agraphical rendering or drawing of both the visible or unobstructedportions of the catheter and the visually obstructed portions of thecatheter.

The present invention is directed to a high density mapping catheter andassociated methods of modeling the catheter on a display outside thepatient's body, the model showing both the unobstructed portions of thecatheter and the visually obstructed portions of the catheter. Inexemplary embodiments, the unobstructed portions of the catheter and thevisually obstructed portions of the catheter are shown different fromone another so that the physician can easily discern which portions areunobstructed and which portions are obstructed. For example, theunobstructed portion of the catheter may be shown as a 3-D rendering,while the visually obstructed portion of the catheter may be shown in“silhouette” form overlaying (or in the foreground, or “on top of”) allother objects being shown on the display. The silhouette is created inpiecewise fashion for only those portions of the catheter boundary thatare obscured. In other examples, the different portions of the cathetermay be different colors, shown as solid versus outline form, etc. In anyevent, the physician is provided with a clear rendering of the entirelength of the catheter that is in the display area.

In accordance with one aspect of the present invention, an electricalmapping system is disclosed for modeling both obstructed andunobstructed portions of a catheter. The system includes a catheter bodycomprising a distal portion and a proximal portion, the catheter bodysupporting a plurality of electrodes electrically connected to an outputdevice. The system also includes a processing component operativelyassociated with the output device. The rendering component receives rawdata from the plurality of electrodes and generates a plurality ofimages based on the raw data. The rendering component overlays theplurality of data images on one another to generate a three-dimensionalimage representing both the internal tissue and an unobstructed portionof the catheter body. The system also includes a visual enhancementcomponent which overlays a silhouette representing at least oneobstructed portion of the catheter body using the positional data forthe catheter body.

In accordance with another aspect of the present invention, a cathetersystem is disclosed for use in electrical mapping of internal tissue.The catheter system includes a catheter body extending between a distaltip and a proximal portion. The catheter body includes a plurality ofmapping electrodes supported in the distal tip for use in acquiringmapping information. A rendering component is configured to generate athree-dimensional image based on the mapping information. Thethree-dimensional image represents an outer boundary of the internaltissue and an unobstructed portion of the catheter body relative to theouter boundary of the internal tissue. A visual enhancement component isconfigured to overlay a silhouette representing at least one obstructedportion of the catheter body on the three-dimensional image.

In accordance with another aspect of the present invention, a method isdisclosed for mapping cardiac tissue and modeling both obstructed andunobstructed portions of an electrode catheter. The method comprisesintroducing the electrode catheter into a chamber of a heart to bemapped, and moving the electrode catheter relative to a surface of theheart, wherein a plurality of electrodes contact the surface of theheart to generate mapping coordinates. The method also comprisesgenerating a three-dimensional image based on the mapping information,the three-dimensional image representing the surface of the heart and anunobstructed portion of the electrode catheter. The method alsocomprises determining which portion of the electrode catheter isobstructed, and overlaying the obstructed portion of the electrodecatheter on the three-dimensional image.

In accordance with another aspect of the present invention, a method isdisclosed for mapping cardiac tissue and modeling both obstructed andunobstructed portions of an electrode catheter. The method comprisesobtaining mapping, coordinates from the electrode catheter inserted intoa chamber of a heart, the mapping coordinates representing a surface ofthe heart. The method also comprises generating a three-dimensionalimage based on the mapping information, the three-dimensional imagerepresenting the surface of the heart and an unobstructed portion of theelectrode catheter. The method also comprises generating a plurality ofcandidate silhouette fragments representing a body of the electrodecatheter, and determining which candidate silhouette fragments areobstructed by other visible objects in the three-dimensional image. Themethod also comprises overlaying the obstructed portion of the electrodecatheter using only those candidate silhouette fragments obstructed byother visible objects in the three-dimensional image.

The foregoing and other aspects, features, details, utilities, andadvantages of the present invention will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a navigation and mapping system inaccordance with the present invention.

FIG. 2 illustrates a catheter being introduced into a patient's heart.

FIG. 3 illustrates a display provided by a navigation and mapping systemin accordance with the present invention.

FIG. 4 illustrates an exemplary embodiment of a high density mappingcatheter in accordance with the present invention.

FIG. 5 is a block diagram illustrating an exemplary embodiment ofcomputer components and program code which may be implemented inaccordance with the present invention.

FIG. 6A-C illustrate exemplary images which may be output on a displayprovided by the navigation and mapping system, wherein a graphicalrendering or drawing of the catheter showing both unobstructed and whatwould otherwise be obstructed portions of a catheter.

FIG. 7 is a flow diagram illustrating exemplary operations which may beimplemented in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 presents a schematic of one embodiment of a medicalnavigation/visualization system 5. The medical navigation/visualizationsystem 5 will be briefly addressed herein, as it is one such system thatmay utilize the mapping electrode functionality that will be addressedin detail below. The medical navigation/visualization system 5 is alsodiscussed in detail in U.S. Patent Application Publication No. US2004/0254437 (published on Dec. 16, 2004) that is assigned to theassignee of this patent application, and the entire disclosure of whichis incorporated by reference in its entirety herein.

The patient 11 is only schematically depicted as an oval for clarity.Three sets of surface or patch electrodes are shown as 18, 19 along aY-axis; as 12, 14 along an X-axis; and 16, 22 along a Z-axis. Patchelectrode 16 is shown on the surface closest to the observer, and patchelectrode 22 is shown in outline form to show its placement on the backof patient 11. An additional patch electrode, which may be referred toas a “belly” patch, is also seen in the figure as patch electrode 21.Each patch electrode 18, 19, 12, 14, 16, 22, 21 is independentlyconnected to a multiplex switch 24. The heart 10 of patient 11 liesbetween these various sets of patch electrodes 18, 19, 12, 14, 16, 22.Also seen in this figure is a representative catheter 13 having a numberof electrodes 17. The electrodes 17 may be referred to as the “rovingelectrodes” or “measurement electrodes” herein. It is noted that anynumber of electrodes may be utilized, generally with more electrodesproviding higher-density mapping. It, is also noted that in use thepatient 11 will have most or all of the conventional 12 lead ECG systemin place as well, and this ECG information is available to the systemeven though it is not illustrated in the figures.

Each patch electrode 18, 19, 12, 14, 16, 22, 21 is coupled to the switch24, and pairs of electrodes 18, 19, 12, 14, 16, 22 are selected bysoftware running on computer system 20, which couples these electrodes18, 19, 14, 14, 16, 22 to the signal generator 25. A pair of electrodes,for example electrodes 18 and 19, may be excited by the signal generator25 and they generate a field in the body of the patient and the heart10. During the delivery of the current pulse, the remaining patchelectrodes 12, 14, 16, 22 are referenced to the belly patch electrode21, and the voltages impressed on these remaining electrodes 12, 14, 16,22 are measured by the analog-to-digital or A-to-D converter 26.Suitable lowpass filtering of the digital data may be subsequentlyperformed in software to remove electronic noise and cardiac motionartifact after suitable low pass filtering in filter 27. In thisfashion, the various patch electrodes 18, 19, 12, 14, 16, 22 are dividedinto driven and non-driven electrode sets. While a pair of electrodes isdriven by the signal generator 25, the remaining non-driven electrodesare used as references to synthesize the orthogonal drive axes.

The belly patch electrode 21 is seen in the figure is an alternative toa fixed intra-cardiac electrode. In many instances, a coronary sinuselectrode or other fixed electrode in the heart 10 can be used as areference for measuring voltages and displacements. All of the raw patchvoltage data is measured by the A-to-D converter 26 and stored in thecomputer system 20 under the direction of software. This electrodeexcitation process occurs rapidly and sequentially as alternate sets ofpatch electrodes 18, 19, 12, 14, 16, 22 are selected, and the remainingmembers of the set are used to measure voltages. This collection ofvoltage measurements may be referred to herein as the “patch data set”.The software has access to each individual voltage measurement made ateach individual patch electrode 18, 19, 12, 14, 16, 22 during eachexcitation of each pair of electrodes 18, 19, 12, 14, 16, 22.

The raw patch data is used to determine the “raw” location in threespaces (X, Y, Z) of the electrodes inside the heart 10, such as theroving electrodes 17. This process is also referred to as“triangulation.” Triangulation is the process of determining thelocation of a point by measuring angles from known points. Opticalthree-dimensional measuring systems use triangulation networks in orderto determine spatial dimensions and the geometry. Output of at least twoof the sensors are considered the point on an object's surface whichdefine a spatial triangle. Within this triangle, the distance betweenthe sensors is the base and is known. By determining the angles betweenthe sensors and the basis, the intersection point, and thus the 3dcoordinate, is calculated from the triangular relations.

If the roving electrodes 17 are swept around in the heart chamber whilethe heart 10 is beating, a large number of electrode locations arecollected. These data points are taken at all stages of the heartbeatand without regard to the cardiac phase. Since the heart 10 changesshape during contraction, only a small number of the points representthe maximum heart volume. By selecting the most exterior points, it ispossible to create a “shell” representing the shape of the heart 10. Thelocation attribute of the electrodes within the heart 10 are measuredwhile the electric field is impressed on the heart 10 by the surfacepatch electrodes 18, 19, 12, 14, 16, 22. The patch data set may also beused to create a respiration compensation value to improve the rawlocation data for the locations of the electrodes 18, 19, 12, 14, 16, 22due to movement of the patient's body (e.g., during breathing.

FIG. 2 shows a catheter 13, which may be a high-density mappingcatheter, as described in more detail below, in the heart 10. Thecatheter 13 has a tip electrode 51 (and may optionally includeadditional electrodes, not visible in the figures). Since theseelectrodes lie in the heart 10, the location process detects theirlocation in the heart 10. While they lay on the surface and when thesignal generator 25 is “off”, each patch electrode 18, 19, 12, 14, 16,22 (FIG. 1) can be used to measure the voltage on the heart surface. Themagnitude of this voltage, as well as the timing relationship of thesignal with respect to the heartbeat events, may be measured andpresented to the cardiologist or technician through the display 23. Thepeak-to-peak voltage measured at a particular location on the heart wallis capable of showing areas of diminished conductivity, and which mayreflect an infracted region of the heart 10. The timing relationshipdata are typically displayed as “isochrones”. In essence, regions thatreceive the depolarization waveform at the same time are shown in thesame false color or gray scale.

FIG. 3 shows an illustrative computer display from the computer system20. The display 23 is used to show data to the physician user and topresent certain options that allow the user to tailor the systemconfiguration for a particular use. It should be noted that the contentson the display 23 can be easily modified and the specific data presentedis only of a representative nature. An image panel 60 shows a geometryof the heart chamber 62 that shows “isochrones” in false color orgrayscale together with guide bar 64 to assist in interpretation. Inthis hypothetical image, the noted mapping methodology has been usedwith a high-density catheter to create a chamber representation that isdisplayed as a contoured image.

The guide bar 64 is graduated in milliseconds and it shows theassignment of time relationship for the false color image in thegeometry. The relationship between the false color on the geometry image62 and the guide bar 64 is defined by interaction with the user in panel66. As shown, the display may also provide traces and other informationrelated to the ECG electrodes, mapping electrodes and referenceelectrodes, as well as other information that may assist the physicians.

As noted above, a significant amount of data is required to generate adetailed image of the cardiac tissue of interest. In order to gatheradequate data more quickly, a high density mapping electrode cathetermay be implemented having a plurality of electrodes. An exemplarycatheter 100 is shown in FIG. 4. The illustrated catheter 100 includes acatheter body or shaft 102 having an electrode tip 108 disposed at adistal end thereof. The catheter 100 further includes a number ofmapping electrode wires 104 terminating in electrodes 106. Theelectrodes 106 can be used to map cardiac tissue, as discussed above.More specifically, a physician can sweep the electrodes 106 acrosstissue to be mapped. In this regard, a large volume of mappinginformation can be obtained quickly when the electrodes 106 come intocontact with the tissue as the catheter 100 is swept across the tissue.

Each of the wires 104 may be threaded through an inner lumen of thecatheter shaft 102. The electrodes 106 then extend through holes formedin the catheter shaft 102 at the desired location. The electrodes 106may be bonded to the shaft 102 at the openings or may otherwise bemaintained in a substantially fixed relationship with respect to theshaft 102.

In exemplary embodiments, the electrodes 106 may be tightly secured tocatheter shaft 102. Alternatively, each of the mapping electrodes may beformed from a nickel titanium fiber with a conductive metallic core suchas platinum. The conductive core of the illustrated fibers serves as theelectrical pathway for the tip electrodes 106 (instead of the wires104). In such an embodiment, the tip electrodes 106 may be formed bymelting an exposed section of the conductive core near the surface ofthe catheter shaft 102.

Generally, the catheter shaft 102 will have a diameter and stiffnessthat is significantly greater than the diameter and stiffness of thewiring 104 provided therein. For instance, the catheter shaft 102 may bea 5 or 7 French (i.e., 0.065 in. or 0.092 in.) catheter. In suchembodiments, the catheter shaft may have a diameter that is at leastfive to ten times (or more) the diameter of the individual wires 104.The size of the catheter shaft 102 may allow the catheter shaft 102 toreadily deflect when the moved (e.g., brushed) over an internal tissuesurface without significant deflection of the catheter shaft 102. Forinstance, the catheter shaft may have a buckle strength (e.g., wherebending is initiated) of no more than about 5 grams and more preferablyno more than about 1-2 grams. Use of such low buckling strength allowsthe end of the catheter shaft 102 to readily conform to a tissue surfacewithout significantly deflecting or otherwise penetrating the tissuesurface. In addition, when the catheter shaft contacts an internaltissue surface, the stiffness of the shaft alerts an operator (e.g.,physician) that the catheter shaft is in contact with patient tissue.

As mentioned above, the inner lumen of the catheter shaft 102 may beused to thread the wiring 104 for the electrodes 106. In addition, forcertain procedures, it may be desired to irrigate the electrodes 106with saline solution, for example, to prevent undesired heating orclotting. A lumen for such irrigation fluid may be formed withincatheter shaft 102 (which can include openings to allow for flow of theirrigation fluid), or the irrigation fluid may be delivered via aseparate lumen associated with other structure of the catheter.

It is desirable to provide an enlarged, generally spherical up of thecatheter. This tip configuration has a number of advantages. First, itis desirable to avoid puncturing of the cardiac tissue in connectionwith contact by the catheter. The enlarged and rounded configuration ofthe tip in this regard provides a larger surface contact area andreduces the pressure on and likelihood of puncturing any cardiac tissuecontacted. In addition, it is desirable to enhance the visibility of thetip, both on the mapping display and in connection with any fluoroscopicimages obtained in connection with the procedure. The enlarged tipimproves impedance and, therefore, visibility with respect to theelectrical navigation system. The increased cross-section also improvesvisibility with respect to the fluoroscopic images.

While the catheter 100 described above with reference to the figuresrepresents an advantageous implementation of the present invention, itwill be appreciated that many other implementations are also possible.

The electrodes 106 can be any of various types of electrodes includingablation electrodes, mapping electrodes, or combination ablation/mappingelectrodes. The illustrated electrodes 106 are mapping electrodes, asbest shown in FIG. 4. The electrodes 106 are divided into a number ofelectrically isolated sections 110, in this case, defining fourquadrants. Because the sections 110 are electrically isolated,independent positioning signals can be obtained with regard to each ofthe sections 110. In this manner the signals from the sections 110 canbe processed to define references, e.g., North, South, East and West,which are useful in guiding movement of the catheter during a medicalprocedure.

FIG. 5 is a block diagram illustrating an exemplary embodiment ofcomputer components and program code which may be implemented inaccordance with the present invention to process the positional ormapping data from the electrodes 106. The mapping data obtained by theelectrodes 106 may be processed using software 200 executable on acomputer system (e.g., the computer system 20 shown in FIG. 1). In anexemplary embodiment, the software 200 may include a rendering component201 and an enhancement component 202, each operatively associated withan output device (e.g., the display 23 in FIG. 1) and computer readablestorage 210. The processing component 201 receives raw data from theelectrodes 106 and generates a plurality of images based on the rawdata. The rendering component 201 may overlay the data images on oneanother to generate a three-dimensional image representing both theinternal tissue and an unobstructed portion of the catheter body.Exemplary output is illustrated in FIG. 6A-C, and discussed in moredetail below.

The enhancement component 202 overlays a silhouette of what wouldotherwise be an obstructed portion of the catheter body 102 using thepositional data for the catheter body 102 (e.g., as can be seen in FIG.6A-C). Operation of the enhancement component 202 may be described asincluding two tasks. First, the enhancement component 202 generatescandidate silhouette fragments, and second the enhancement component 202displays only those candidate fragments that are obscured or obstructedby other objects in the scene output on the display 23.

The first task may be accomplished using the same triangulation datathat are used to produce the three-dimensional image of the catheter(e.g., as used by the processing component 201). The triangles arejoined edge-to-edge to form a closed volume that approximates veryclosely the true shape of the body of the catheter. Candidate silhouettefragments are those edges shared between two triangles, one with itsoutward side pointing toward the physician's field of view, and theother with its outward side pointing away from the physician's field ofview.

Each of the candidate edges may be compiled into a list 211 for furtherprocessing. Additional edges may be added in special cases. One suchspecial case may include when the edge separates a catheter electrode106 from the catheter body 102 and at least one of the adjacenttriangles has an outward side pointing toward the physician's field ofview. Another such case may include when the edge is at the end of thecatheter body 102 and the end plane has its outward side pointing towardthe physician's field of view. Another such case may include when theedge is at the end of the catheter body 102 and the adjacent trianglehas its outward side pointing toward the physician's field of view.

The second task may be accomplished by applying a graphics depth buffer212. Each edge in the list of candidate silhouette fragments is firstoffset away from the center of the catheter body 102 by a distance inthe model space corresponding to one pixel on the display 23. Thisavoids the possibility of the edge being obscured by the same catheterbody 102 that generated the edge. The edge is then drawn into a framebuffer 213 using a depth mask that allows drawing of a pixel only if thedepth is greater than the current depth.

After completing these tasks, the visual enhancement component is ableto overlay a silhouette representing at least one obstructed portion ofthe catheter body using the positional data for the catheter body. FIG.6A-C illustrate exemplary images 250 a-c which may be output on adisplay provided by the navigation and mapping system, such as thedisplay 23 shown in FIGS. 1 and 3. In FIG. 6A-C, a graphical renderingof the catheter 100 includes both an unobstructed portion 252 a-c(respectively in FIG. 6A-C) and portion 255 a-c of the catheter 100 thatwould otherwise be obstructed from view (e.g., behind the heart wall).Accordingly, the physician is able to view an image of the entire lengthof the catheter 100 which is within the area being displayed.

In FIG. 6A-C, both the unobstructed portions 252 a-c (respectively) ofthe catheter 100, and the obstructed portion(s) 255 a-c are shown (i.e.,those portions 255 a-c are visible in the 3-D images 250 a-c that wouldotherwise be obstructed by the heart wail). As discussed above, theportion of the catheter 100 that would otherwise be obstructed by theheart wall may be identified by the enhancement component by comparing adepth coordinate of the catheter 100 to a depth coordinate of thesurface of the heart 10, and then overlaying silhouettes 255 a-crepresenting the obstructed portion(s) of the catheter 100 only when thedepth coordinate of the catheter 100 is greater than the depthcoordinate for the surface of the heart 10.

In FIGS. 6B and 6C it is further seen that more than one catheter 100and 100′ is shown in the 3-D images 250 a-c. However, the rendering ofthe obstructed portion(s) 255 b, 255 e (respectively) are shown for theactive catheter (i.e., the catheter that the physician is currentlymoving). In other embodiments, however, a graphical rendering may beshown for the obstructed portion(s) of more than one of the catheters(e.g., for both catheters 100 and 100′).

It is noted that in FIG. 6A-C, the unobstructed portions 252 a-c of thecatheters are shown as being shaded so as to appear as athree-dimensional object, and the obstructed portions 232 a-c are shownas silhouettes or outlines. However, any suitable differentiation may beused, such as but not limited to, different colors or different shadingfor the portions 252 a-c and 255 a-c.

Before continuing, it is also noted that in each of these images 250a-c, the output may be updated in real-time or substantially inreal-time. Accordingly, the physician is able to view the images 250 a-cas the catheter 100 is being moved and positioned at the desiredlocation within the heart 10.

FIG. 7 is a flow diagram illustrating exemplary operations which may beimplemented in accordance with the present invention. Operations 300 maybe embodied as logic instructions on one or more computer-readablemedium. When executed on a processor, the logic instructions cause ageneral purpose computing device to be programmed as a special-purposemachine that implements the described operations. In an exemplaryimplementation, the components and connections depicted in the figuresmay be used for brokering creative content online.

Operations 300 illustrate an exemplary method for mapping cardiac tissueand modeling an obstructed view of an electrode catheter. In operation310, mapping coordinates are obtained from an electrode catheterinserted into a chamber of a heart, where the mapping coordinatesrepresenting a surface of the heart. In operation 311, athree-dimensional image is generated based on the mapping information,where the three-dimensional image shows the surface of the heart and anunobstructed portion of the electrode catheter. In operation 312, aplurality of candidate silhouette fragments is generated representing abody of the electrode catheter. In operation 313, a determination ismade which candidate silhouette fragments are obstructed by othervisible objects in the three-dimensional image. And in operation 314,the obstructed portion of the electrode catheter is overlaid on thethree-dimensional image using, only those candidate silhouette fragmentsdetermined to be obstructed by other visible objects in thethree-dimensional image.

The operations shown in FIG. 7 and described herein are provided forpurposes of illustration. It is noted that the operations are notlimited to the ordering shown. Still other operations may also beimplemented.

Although exemplary embodiments of this invention have been describedabove with a certain degree of particularity, those skilled in the artcould make numerous alterations to the disclosed embodiments withoutdeparting from the spirit or scope of this invention.

All directional references (e.g., upper, lower, upward, downward, left,right, leftward, rightward, top, bottom, above, below, vertical,horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentinvention, and do not create limitations, particularly as to theposition, orientation, or use of the invention. Joinder references(e.g., attached, coupled, connected, and the like) are to be construedbroadly and may include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relation to each other. It is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative only and not limiting.Changes in detail or structure may be made without departing from thespirit of the invention as defined in the appended claims.

1. An electrical mapping system for internal tissue, the electricalmapping system modeling both obstructed and unobstructed portions of acatheter, comprising: a catheter body comprising a distal portion and aproximal portion, the catheter body supporting a plurality of electrodeselectrically connected to an output device; a rendering componentoperatively associated with the output device, the rendering componentreceiving raw data from the plurality of electrodes and generating aplurality of images based on the raw data, the rendering componentoverlaying the plurality of data images on one another to generate athree-dimensional image representing both the internal tissue and avisible portion of the catheter body; and an enhancement componentconfigured to overlay a silhouette on the three-dimensional image, thesilhouette representing at least one obstructed portion of the catheterbody using the positional data for the catheter body.
 2. The system ofclaim 1, wherein the enhancement component generates candidatesilhouette fragments and displays only those candidate silhouettefragments obstructed by other visible objects.
 3. The system of claim 2,wherein other visible objects include portions of the internal tissue.4. The system of claim 2, wherein other visible objects include displaygraphics.
 5. The system of claim 2, wherein other visible objectsinclude labels, lesions, anatomical markers, and other catheters.
 6. Thesystem of claim 1, wherein the enhancement component overlays asilhouette on the three-dimensional image of the at least one obstructedportion of a plurality of catheters.
 7. The system of claim 1, whereinthe enhancement component graphically illustrates at least oneobstructed portion of an active catheter.
 8. The system of claim 1,wherein the enhancement component graphically illustrates an outerboundary of the at least one obstructed portion of the catheter body. 9.The system of claim 1, wherein the enhancement component usestriangulation data used by the rendering component.
 10. The system ofclaim 1, wherein the enhancement component applies a depth buffer toidentify an outer boundary of the at least one obstructed portion of thecatheter body.
 11. The system of claim 10, wherein the enhancementcomponent only draws the outer boundary of the at least one obstructedportion of the catheter body if a depth coordinate of the catheter bodyis greater than a depth coordinate for the internal tissue being shown.12. A catheter system for use in electrical mapping of internal tissue,comprising: a catheter body extending between a distal tip and aproximal portion, the catheter body including a plurality of mappingelectrodes supported in the distal tip for use in acquiring mappinginformation; a rendering component configured to generate athree-dimensional image based on the mapping information, thethree-dimensional image representing an outer boundary of the internaltissue and a visible portion of the catheter body relative to the outerboundary of the internal tissue; and an enhancement component configuredto overlay a silhouette of at least one obstructed portion of thecatheter body on the three-dimensional image, the obstructed portion ofthe catheter body overlayed as the silhouette being obstructed by theouter boundary of the internal tissue.
 13. A method for mapping cardiactissue and modeling both unobstructed and obstructed portions of anelectrode catheter, comprising: introducing an electrode catheter into achamber of a heart to be mapped, and moving the electrode catheterrelative to a surface of the heart, wherein a plurality of electrodescontact the surface of the heart to generate mapping coordinates;generating a three-dimensional image based on the mapping information,the three-dimensional image representing the surface of the heart and anunobstructed portion of the electrode catheter; determining whichportion of the electrode catheter is obstructed; and overlaying asilhouette representing at least one obstructed portion of the electrodecatheter in the three-dimensional image.
 14. The method of claim 13,wherein moving the electrode catheter comprises sweeping the electrodecatheter over the surface of the heart.
 15. The method of claim 13,further comprising: generating a plurality of candidate silhouettefragments representing the electrode catheter; and displaying only thecandidate silhouette fragments obstructed by other visible objects. 16.The method of claim 13, further comprising using triangulation data forgenerating the three-dimensional image and overlaying the at least oneobstructed portion of the electrode catheter on the three-dimensionalimage.
 17. The method of claim 13, further comprising applying a depthbuffer to identify the at least one obstructed portion of the electrodecatheter.
 18. The method of claim 13, further comprising comparing adepth coordinate of the electrode catheter to a depth coordinate of thesurface of the heart.
 19. The method of claim 18, further comprisinggraphically illustrating the at least one obstructed portion of theelectrode catheter only when the depth coordinate of the electrodecatheter is greater than the depth coordinate for the surface of theheart.
 20. The method of claim 13, further comprising overlaying thesilhouette representing the at least one obstructed portion of theelectrode catheter only when the electrode catheter is facing toward auser.